Most refrigeration systems are not 100% free of leaks. Thus, the amount (or mass) of refrigerant within the refrigeration system decreases over time. Refrigeration systems, however, are designed to operate with a specific amount of refrigerant. Therefore, loss of refrigerant in a refrigeration system over time typically reduces the efficiency of the refrigeration system. Also, if the amount of refrigerant in the refrigeration system drops to a certain level, the refrigeration system may cease to operate and/or be damaged. For these reasons, a common maintenance operation for a refrigeration system is to recharge the refrigerant.
The recharging operation typically involves evacuating the refrigeration system of any remaining refrigerant and, if present, other materials. Once the refrigeration system is evacuated, a predetermined amount of new refrigerant is re-introduced. A refrigerant source, typically a large tank of refrigerant, is connected to the refrigeration system of a vehicle through a line. The tank includes a control valve where the line connects to the tank, and introduction of refrigerant into the refrigeration system is controlled by the control valve on the tank.
This conventional charging system, however, suffers from several problems. A refrigeration system is designed to operate with a specific amount of refrigerant, and too little or too much refrigerant can reduce the effectiveness of the recharging operation. For example, the amount of refrigerant that leaves the refrigerant source (i.e., tank) may not be equal to the amount of refrigerant that is introduced into the refrigeration system because a certain amount of the refrigerant remains in the line between the refrigerant source and the refrigeration system. Depending upon the length of the line and the temperature and pressure of the refrigerant in the line, the amount of refrigerant within the line may vary. Thus, a technician is not able to accurately and consistently determine the amount of refrigerant being introduced into the refrigeration system based upon a measurement of refrigerant leaving the refrigerant source.
Another issue with a conventional charging system is that once the line is disconnected from the refrigeration source, any refrigerant within the line is evacuated into the atmosphere. Depending upon type of refrigerant, this can be both wasteful and hazardous. Furthermore, recent advances in refrigeration technology employ carbon dioxide as the refrigerant, which is stored at a pressure as much as ten times higher than the pressure at which conventional refrigerants are stored; and because of the high pressure, the release of any gas remaining within the line into the atmosphere can be dangerous. There is, therefore, a need for a refrigerant charging system and method that is more accurate, safer, and less wasteful than conventional refrigeration charging systems, particularly when the refrigerant is carbon dioxide.